The invention relates to a soot-filtering unit for the exhaust gas section of a diesel internal combustion engine with a supercharging device, i.e., a so-called supercharged diesel internal combustion engine. The soot-filtering unit includes at least one soot filter placed in an exhaust gas pipe and a regeneration device with at least one burner.
In my own older U.S. patent application Ser. No. 196,558, filed on May 20, 1988, a soot filter unit for the exhaust of a diesel internal combustion engine is disclosed. In the unit of this earlier application, the burner of a regeneration device is operated with the exhaust gas from the diesel internal combustion engine as its combustion air supply. However, it now appears that, under certain operating conditions, the engine performance characteristics of the diesel internal combustion engine may result in the oxygen content of the exhaust gas becoming insufficient for reliable functioning of the burner. Further, there also is the potential problem that the gas generated by the burner and used for regeneration of the soot filter will not contain enough oxygen for the combustion of the soot necessary to produce regeneration of the soot filter. These comments also apply to the exhaust gas unit of my U.S. patent application Ser. No. 196,557, that was also filed on May 20, 1988.
On the other hand, it has already been suggested, for example, from U.S. Pat. No. 4,345,431 and German Offenlegungsschrift No. 32 04 176, that a burner of a regeneration device be operated with combustion air that is supplied from an external source. However, such devices require relatively high combustion air supply pressures which necessitate the provision of additional compressors or blowers to supply the combustion air. The need for such a blower or compressor increases the cost for such a soot-filtering device and such a blower or compressor also increases operating expenses due to the relatively high power it consumes to function.
In recent years, in the field of diesel internal combustion engines, supercharging has been used to an increasing extent, and by which air that is under a boost pressure is fed to the cylinders of the internal combustion engine. A common form of supercharging device comprises a turbine in the exhaust gas section of the diesel internal combustion engine which is coupled to a compressor whose outlet is connected to the air intake pipe or pipes of the diesel engine. This form of supercharging is also commonly known as turbocharging and it enables higher performance and an improved combustion efficiency to be obtained.